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Analog Devices Inc. LT3991EDD#TRPBF
- Part No.:
- LT3991EDD#TRPBF
- Manufacturer:
- Analog Devices Inc.
- Package:
- 10-WFDFN Exposed Pad
- Datasheet:
-
LT3991EDD#TRPBF.pdf
- Description:
- IC REG BUCK ADJ 1.2A 10DFN
- Quantity:
- Payment:
- Shipping:
Inventory:7,986
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Product details
Overview
LT3991EDD#TRPBF from Analog Devices (formerly Linear Technology) is a 55V, 1.2A monolithic step-down DC/DC regulator in a 3mm × 3mm DFN-10 package with exposed pad. It delivers ultralow 2.8µA quiescent current in regulation, supports adjustable switching frequency from 200kHz to 2MHz, and integrates a 0.44Ω NPN switch, boost Schottky diode, and internal compensation. It is used in automotive battery regulation and portable power supplies where low standby power and wide VIN range are critical.
For engineers reviewing the LT3991EDD#TRPBF datasheet, LT3991EDD#TRPBF pinout, LT3991EDD#TRPBF application, or LT3991EDD#TRPBF equivalent, key selection factors include its 4.3V–55V input range, 1.19V feedback reference, 91% power-good threshold, and Burst Mode operation delivering <15mV output ripple at no load - all validated for –40°C to 125°C junction temperature.
Technical Context
The LT3991EDD#TRPBF employs constant-frequency current-mode control with internal slope compensation and an RS flip-flop–driven bipolar NPN switch. Its VC node is clamped by both soft-start voltage and active current-limit circuitry, enabling fast transient response and stable loop behavior across wide duty cycles.
Operation includes automatic transition to low-ripple Burst Mode below ~86mA load, reducing input supply current to 1.7µA in sleep periods while maintaining regulation. Frequency foldback activates when FB voltage drops during startup or overload, limiting peak inductor current and improving fault robustness.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 4.3V to 55V - supports direct connection to 12V/24V/48V automotive and industrial rails without pre-regulation. |
| Quiescent Current (IQ) | 2.8µA at no load - enables >10-year battery life in always-on IoT sensors and telematics modules. |
| Max Output Current | 1.2A continuous - sufficient for powering microcontrollers, CAN transceivers, and sensor signal chains. |
| Switching Frequency | 200kHz to 2MHz (RT-programmable) - allows tradeoff between small magnetics (high fSW) and high efficiency (low fSW). |
| Feedback Reference | 1.19V ±15mV - enables precise output programming from 1.19V to 30V using external resistor divider. |
| Power Good Threshold | 91% of regulated VOUT - provides reliable system reset signaling with 20mV hysteresis for noise immunity. |
| Enable Threshold | 1.01V rising, 0.975V falling - ensures clean shutdown with 30mV hysteresis; valid only when VIN > 4.3V. |
Pinout & Package
LT3991EDD#TRPBF is housed in a thermally enhanced 10-lead (3mm × 3mm) plastic DFN package with exposed pad (Pin 11), which must be soldered to PCB ground for thermal and electrical performance. θJA = 45°C/W, θJC = 10°C/W.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| BD (1) | Boost Diode Anode | Connects to cathode of external Schottky diode; forms charge pump path for BOOST drive voltage. |
| BOOST (2) | Bootstrap Drive | Supplies >VIN voltage to saturate internal NPN switch; requires external capacitor to SW. |
| SW (3) | Switch Node | Drives inductor and catch diode; carries high di/dt; requires tight layout and low-inductance routing. |
| VIN (4) | Main Power Input | Supplies IC bias and switch current; must be locally bypassed with low-ESR ceramic capacitor. |
| EN (5) | Enable Control | Hysteretic shutdown input; draws <20nA; ties to VIN if always-on operation required. |
| FB (6) | Feedback Sense | Regulated to 1.19V; connects to resistor divider tap; requires 10pF phase-lead cap to VOUT for stability. |
| SS (7) | Soft-Start Control | Controls inrush current via external RC ramp; discharged only when EN is low. |
| RT (8) | Frequency Set | Resistor-to-ground sets switching frequency from 200kHz to 2MHz per datasheet table. |
| PG (9) | Power Good Flag | Open-drain output asserting high when VOUT reaches 91% of target; requires external pull-up. |
| SYNC (10) | External Clock Sync | Ground for Burst Mode; accept 250kHz–2MHz clock for synchronized pulse-skipping operation. |
Key Features
| Feature | Design Value |
|---|---|
| Ultralow Quiescent Current | 2.8µA IQ regulating 12VIN to 3.3VOUT - extends battery runtime in always-on monitoring systems. |
| Low-Ripple Burst Mode | Output ripple <15mVP-P at no load - eliminates audible noise and EMI concerns in sensitive analog circuits. |
| Integrated Boost Diode | On-die Schottky reduces BOM count and improves reliability vs. discrete boost diode solutions. |
| Internal Compensation | Eliminates external compensation network - simplifies design and reduces footprint for space-constrained layouts. |
| Saturating Switch Design | 0.44Ω on-resistance NPN switch - delivers high efficiency (>90% at 1A, 12VIN→3.3VOUT) without MOSFET gate drive complexity. |
| Thermally Enhanced DFN | 3mm × 3mm package with exposed GND pad - achieves θJC = 10°C/W for high-power density in compact enclosures. |
Applications
| Automotive Battery Regulation | Portable Medical Instrumentation |
|---|---|
Use Scenario: Powering infotainment head units and ADAS camera modules from 12V vehicle battery with cold-crank tolerance down to 4.3V. IC Role / Device Role / Timing Role: Primary buck regulator providing stable 3.3V/5V rail; handles load dump transients up to 55V. Use Value: 2.8µA quiescent current prevents battery drain during vehicle off-state; PG flag enables safe MCU boot sequencing. |
Use Scenario: Supplying ultra-low-power glucose meters and wearable ECG monitors operating from coin-cell batteries. IC Role / Device Role / Timing Role: Main power converter delivering regulated 3.3V to ADC, BLE SoC, and display driver with minimal standby loss. Use Value: Burst Mode maintains <15mV ripple while drawing only 2.8µA - enabling multi-year operation on CR2032 cells. |
| Industrial Sensor Transmitters | Remote Telematics Gateways |
Use Scenario: Powering 4–20mA loop-powered pressure/temperature transmitters in hazardous area field devices. IC Role / Device Role / Timing Role: Secondary regulator deriving isolated 3.3V logic rail from loop supply; operates across 9–55V input range. Use Value: Wide VIN and internal compensation reduce component count; SS pin enables controlled inrush during hot-swap events. |
Use Scenario: Providing primary 5V rail to LTE/GNSS modules in fleet tracking units mounted in vehicles with unstable battery voltage. IC Role / Device Role / Timing Role: High-efficiency buck converter supporting 1.2A peak loads during data transmission bursts. Use Value: 1.2A output capability and RT-programmable frequency allow optimization for size (2MHz) or efficiency (400kHz) per mechanical constraints. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar step-down regulator applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| LT8609SIV#TRPBF | 42V max VIN, 2A output, 2.5µA IQ, integrated MOSFETs, requires external bootstrap cap | Better suited for higher-current, lower-VIN apps; lacks internal Schottky diode | Select when >1.2A output or synchronous rectification is required; verify thermal margin in DFN-10 footprint. |
| TPS54202DRCT | 42V max VIN, 2A output, 2µA IQ, integrated MOSFETs, 100% duty cycle support | Lower max VIN; no internal boost diode; different enable threshold (1.23V) | Prefer for cost-sensitive industrial designs needing 100% dropout; confirm PG functionality matches system reset timing. |
Compared with LT3991EDD#TRPBF, LT8609SIV#TRPBF offers higher current and lower IQ but requires external bootstrap capacitance and lacks integrated boost diode; TPS54202DRCT provides 100% duty cycle and lower cost but sacrifices 55V rating and internal Schottky integration - making LT3991EDD#TRPBF optimal for high-input-voltage, low-quiescent-current, single-chip simplicity.
Availability
LT3991EDD#TRPBF is available at Aetrix Electronics and suitable for automotive battery regulation, portable medical instrumentation, and industrial sensor transmitters requiring stable component supply across extended temperature ranges.
Supply support for LT3991EDD#TRPBF includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.
Manufacturer
Analog Devices acquired Linear Technology in 2017 and maintains full product support, documentation, and manufacturing continuity for the LT3991 family.
The LT3991 series was designed for high-reliability, wide-input-voltage DC/DC conversion in automotive, industrial, and portable applications demanding ultralow quiescent current and robust fault handling.
FAQ
What is the maximum input voltage rating for LT3991EDD#TRPBF?
The LT3991EDD#TRPBF has an absolute maximum VIN rating of 55V, with guaranteed operation from 4.3V to 55V. At input voltages above the calculated VIN(OP-MAX) - determined by switching frequency and minimum on-time - the device enters pulse-skipping mode, increasing output ripple but maintaining regulation. For sustained 55V operation, use ≤400kHz switching frequency per the datasheet's VIN(OP-MAX) equation.
Does LT3991EDD#TRPBF require an external Schottky diode?
No, the LT3991EDD#TRPBF integrates a boost Schottky diode on-die connected to the BD pin. This eliminates the need for an external boost diode in the bootstrap circuit. However, an external catch diode (e.g., DFLS2100) is still required between SW and VOUT for flyback energy recirculation - the internal Schottky serves only the BOOST drive path, not the main power path.
How does the LT3991EDD#TRPBF achieve 2.8µA quiescent current?
The LT3991EDD#TRPBF achieves 2.8µA quiescent current through low-ripple Burst Mode operation: during light loads, it delivers discrete current pulses to the output capacitor followed by extended sleep periods where most internal circuitry is powered down. In sleep, only essential bias currents remain active, drawing just 1.7µA; the 2.8µA figure reflects average current including brief active pulses under typical no-load conditions.
Can LT3991EDD#TRPBF be synchronized to an external clock?
Yes, the LT3991EDD#TRPBF supports external synchronization via the SYNC pin (Pin 10), accepting clocks from 250kHz to 2MHz. When synchronized, it operates in pulse-skipping mode at light loads instead of Burst Mode, increasing quiescent current to ~1.5mA but enabling deterministic timing for EMI reduction. For lowest IQ, ground SYNC to retain Burst Mode operation.
What is the function of the SS pin on LT3991EDD#TRPBF?
The SS (soft-start) pin on LT3991EDD#TRPBF controls inrush current by ramping the internal current limit during startup. An external RC network (e.g., 100kΩ + 10nF) between SS and GND generates a controlled voltage ramp, limiting peak switch current and preventing output overshoot or input rail sag. The SS pin is only actively discharged when EN is low, ensuring repeatable soft-start behavior on each enable cycle.
LT3991EDD#TRPBF Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Analog Devices Inc.
- Series:
- -
- Package/Case:
- 10-WFDFN Exposed Pad
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Function:
- Step-Down
- Output Configuration:
- Positive
- Topology:
- Buck
- Output Type:
- Adjustable
- Number of Outputs:
- 1
- Voltage - Input (Min):
- 4.3V
- Voltage - Input (Max):
- 55V
- Voltage - Output (Min/Fixed):
- 1.19V
- Voltage - Output (Max):
- 30V
- Current - Output:
- 1.2A
- Frequency - Switching:
- 200kHz ~ 2MHz
- Synchronous Rectifier:
- No
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 10-DFN (3x3)
LT3991EDD#TRPBF FAQ
1.How can I place an order for LT3991EDD#TRPBF through Aetrix?
Please submit a Request for Quotation (RFQ) for LT3991EDD#TRPBF on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.
2.Are the price and stock information for LT3991EDD#TRPBF reliable?
The price and inventory of LT3991EDD#TRPBF are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LT3991EDD#TRPBF is usually 5 days.
3.What payment methods are accepted for LT3991EDD#TRPBF?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LT3991EDD#TRPBF transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LT3991EDD#TRPBF?
LT3991EDD#TRPBF orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LT3991EDD#TRPBF order is processed, you will receive an email with the shipment details and tracking number.
Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.
5.How can I obtain technical support or documentation for LT3991EDD#TRPBF?
For technical support, including LT3991EDD#TRPBF datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LT3991EDD#TRPBF requirements.
6.How does Aetrix verify that LT3991EDD#TRPBF is sourced from the original manufacturer or authorized distributors?
All LT3991EDD#TRPBF products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that LT3991EDD#TRPBF meets industry standards.
7.What is the process for return or replacement of LT3991EDD#TRPBF?
All LT3991EDD#TRPBF units undergo pre-shipment inspection (PSI). If there is an issue with LT3991EDD#TRPBF, returns or replacements are accepted under the following conditions:
1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.
2.The issue is reported within 90 days of delivery.
3.The LT3991EDD#TRPBF part is unused and in its original packaging.
Return procedure for LT3991EDD#TRPBF:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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